Valve system for hydraulic press circuits



Feb. 22, 1949. I s gew c 2,462,815 C VALVE SYSTEM FOR HYDRAULIC PRESSCIRCUITS Filed June 26, 1944 IN VEN TOR.

Patented Feb. 1949 VALVE SYSTEM FOR HYDRAULIC PRESS CIRCUITS Robert K.Sedgwick, Chicago, 11]., auignor to American Steel Foundries, Chicago,111., a corporation of New Jersey Application June 26, 1944, Serial No.542,095

Claims.

1 My invention relates to hydraulic machinery and more particularly tonovel hydraulic actuating means therefor.

The general object of my invention is to design a sensitive hydrauliccircuit by means of which the associated. mechanism is capable ofapplying pressure to a work piece in an amount proportionate to thepressure I exerted by the operator, thus enabling the operator to feelthe pressure directly without constant reference to 8. 89.1188.

Another object of my invention is toeliminate the necessity for a servoor follow-up control in a circuit of the above type, thereby-preventingbacklash or looseness in the control mechanism which, as will be readilyunderstood by those skilled in the art, frequently causes a conditionwherein the ram fails closely to follow the handle.

Still another object of my invention is to simplify a circuit of theabove type, thereby reducing the manufacturing costs thereof while, atthe same time, maintaining the sensitivity thereof.

In the drawings, Figure 1 is a somewhat diagrammatic view of a hydraulicpress-with my novel sensitive circuit connected thereto, and Figure 2 isa sectional view taken through one of the valves in my novel system.

Describing my invention in detail, the press which is fragmentarilyillustrated includes 2. cylinder 2 with a ram 4 reciprocal therewithin,said ram having ahead 6 slidably fitted within the cylinder in the usualmanner and defining therewith a main pressure chamber 8 above the I headand an annular pull-back chamber In below the head. A platen indicatedat I2 is mounted on the lower end of the ram. it will .-be understood bythose skilled in the art that if desired, the pull-back chamber l0 maybe eliminated and one or more relatively small pull-back rams andassociated cylinders may be utilized for pulling the platen l2 upwardlyto its retracted position.

My novel hydraulic circuit comprises a supply line I4 connected to areservoir tank It containing a quantity of any suitable hydraulicactuating fluid, such as oil, and a pump it of conventional form ismounted in the 'line l4. A relief valve is provided, said valve being ofconventional form and being adapted to discharge into the tank 16through the relief line 22 at a predetermined maximum pressure, thuspreventing the building up of dangerous pressures in the circuit by thepump l8.

The line H is connected to a pull-back oper. atlng valve 24, the chamber26 of which is connected to the pull-back chamber In by means of thepull-back supply line 28.. The chamber 26 is also connected by a port inthe valve 24 to apipe N which is connected to the internal chamber ofthe operating valve'fl which is substantially identical in constructionwith the valve 24. The valve 24 comprisesa stem 34 which is urged to itsclosed position by means of a spring 38 actuatedby a plunger 38 in themanner hereinafter described.

The'internal chamber of the valve 32 is connected to the main cylinderchamber 8 by a pipe 40 forming a part of the supply line 14, and thechamber of the valve 32 is also connected by means of a discharge pipe42 to the tank IS;

The control lever 44 is afiorded a fixed pivot at 46 intermediate itsends and is provided on one end thereof with a ball-like handle 48 andon the opposite end thereof with a counterweight 50 serving a purposehereinafter described in connection with the operation of the system.When the control lever 44 is in its neutral position, as shown in thedrawing, the lever is approximately horizontal so that pressure isapplied to neither of the operating valves 24 or 32. The pump isoperable to circulate hydraulic fluid in the systemthrough the supplyline I 4 into the l6. This is possible inasmuch as pressure is not iapplied at this point to either of the valves; thus permitting them toopen the ports communicating with the pipes 30 and 42 respectively.

Whenthe operator desires to bring the press ram down upon the work hegrasps the ball handle 48 and pulls it down, thereby applying pressureto the spring stem 52 of the valve 32, said stem being operable to applypressure to the associated spring, thus moving its actuated stem intoclosed position restricting discharge of hydraulic fluid through thedischarge pipe 42. This causes the hydraulic fluid to flow through thepipe 40 into the main cylinder chamber 8 to build up pressuretherewithin sufllclent to move the ram 4 downwardly to engage the platen12 with the work. It will be understood that the ram is moved downwardlyagainst the pressure within the pull-back chamber I0 which is ofsubstantially less cross-sectional area than that of the chamber 8 sothat the difierential between the two chambers permits actuation of theram to its advanced position.

When the platen l2 comes into contact with the work piece it may stopbecause of insufflcient pressure in the chamber 8 to accomplish the workdesired. In this event, the operator exerts additional pressuredownwardly on the handle 48, thereby increasing the pressure on, thespring within the valve 32 and consequently increasing the pressurewithin the chamber 8, as will be clearly understood by those skilled inthe art. It may be noted that by means ofthis arrangement, the operatorcan feel" the resistance of the work in the same manner as if he wereaccomplishing it directly by means of a crowbar or a lever. I

When the working stroke has been completed, the ram 4 is returned to itsretracted position by raising the handle 48, thus pivoting the lever 44clockwise about the pivot point 46 and exerting pressure against theplunger 38. This compresses the spring 36, thereby urging the spindle 34to \its closed position to prevent passage of fluid within the systemthrough the pipe 30. Thus, the fluid is urged through the pull-backsupply pipe 28 into the pull-back chamber l0, and the ram is movedupwardly urging the fluid within the chamber 8 back through the pipe 40and the valve 32 through the discharge pipe 42 into-the tank l6. At thispoint, the operator. may release the handle 48 and the counterweight 50is still operable to exert a slight pressure on the plunger 38, therebymaintaining a slight pressure in the pull-back line 28 and the pull-backchamber ID in order to prevent the ram 4 from' creeping downwardly byforce of gravity.

It will be readily apparent to those skilled in the art that if desired,the counterweight 50 may be eliminatedand a conventional holding valvemaybe mouned in the line 28 to prevent the above-mentioned downwardcreeping of the ram 4 from its retracted position, and in this event,the valve 24 need not necessarily be of the spring actuated typeillustrated, but may be of any conventional design adapted to closeimmediately and positively upon application thereto of pressure by thelever 44. 1

It is to be understood that I do not wish to be limited by the exactembodiment of the device shown which is merely by way of illustrationand .not limitation as various and other forms of the device will, ofcourse, be apparent to those skilled in the art without departing fromthe spirit of the invention or the scope of the claims.

I claim:

1. In an hydraulic press, a cylinder, a ram reciprocal herewithin andhaving a head slidably, fitted therein, a main pressure chamber in saidcylinder at one side of said head, an annular pullback pressure chamberdefined by said cylinder and said ram at the opposite side of said head,and a hydraulic circuit comprising a reservoir, tank, a pair ofoperating valves each having an inlet chamber and a discharge port, apump, drawing liquid from said tank and delivering it to the chamber ofone valve and through said chamber to the pull-back chamber, aconnection from the discharge port of said one valve to the inletchamber of the other valve, said other valve having its chamberconnected to said main chamber and also connected through its dis-jcharge portto said tank, a 'valve stem in each valve for closing theport therein, spring means for moving said stems to their closedpositions,; and operating means for alternately stressing the} springmeans of respective valves, said operating; means comprising a controllever operatively as-; sociated with said spring means, and a counter-jweight on said lever for normally exerting a slight stress on the springmeans associated with the 4 g said one valve, each of said valves havingfluid passages therein enabling fluid under pressure from the associatedpressure chamber to move the stem of the associated valve to openposition against the action of said spring means upon partial orcomplete release of stresses on said spring means.

2. In an hydraulic machine comprising hydraulic motor means includingmain and pullback cylinder chambers and ram means reciprocaltherewithin, said pull-back chamber having less cross-sectional areathan said main chamber, the combination of a reservoir tank, a pumphaving its suction side connected thereto, valve means connected to saidmain chamber and to said tank, said valve means being adapted in itsclosed position to prevent flow of fluid therethrough to said tank whilepermitting flow of fluid to said main chamber, pull-back valve meansconnected to said pull-back chamber and to said first-mentioned valvemeans, said pull-back valve means being adapted in its closed positionto prevent flow of fluid therethrough to said firstmentioned valve meanswhile permitting flow of fluid to said pull-back chamber, a connectionbetween said pull-back valve means and said pump, and means foralternately actuating, said first and second-mentioned valve means, saidactuating means including compression spring means for urging each valvemeans to its closed position, and a manually operable lever adapted toexert direct compressive'forces on said spring means, each of said valvemeans having fluid passages therein enabling fluid under pressure fromthe associated chamber to open the associated valve means against theaction of said spring means.

3. In an hydraulic machine of the class described comprising hydraulicmotor means including main and pull-back cylinder chambers and ram meansreciprocal therewithin, said pull- 1 back chamber being of lesscross-sectional area than said main chamber, the combination of ahydraulic circuit comprising a reservoir tank, a pump having its suctionside connected thereto, a pull-back valve connected to the dischargeside of said pump and connected to said pull-back chamber, an operatingvalve .connected to a port in said first-mentioned valve and comprisinga port connected to said tank, said operating valve being connected tosaid main chamber, a stem in each valve for closing the port therein,resilient actuating means associated with said actuating means ofrespective valves, said operating means comprising a lever pivotedintermediate its extremities, and means operatively connecting saidlever to said resilient means, each of said valves having fluid passagestherein enabling fluid under pressure from the associated pressurechamber to move the stem of the associated valve to open positionagainst the action of said resilient means.

4. In an hydraulic press, a cylinder, a ram reciprocal therewithin andhaving a head slidably fitted therein, a main pressure chamber in saidcylinder at one side of said head, an annular pullback pressure chamberdefined by said cylinder and said ram at the opposite side of said head,and a hydraulic circuit comprising a reservoir tank, a pair of operatingvalves each having an inlet chamber and a discharge port, a pump to thechamber of one valve and through said chamber to the pull-back chamber,a connection from the discharge port of said one valve to the inletchamber of the other valve, said other valve having its chamberconnected to said main chamber and also connected through its dischargeport to said tank, a valve stem in each valve for closing the porttherein, spring means for moving said stems to their closed positions,and operating means for alternately stressing the spring means ofrespective valves, each of said valves having fluid passages thereinenabling fluid under pressure from the associated pressure chamber tomove the stem of the associated valve to open position against theaction of said spring means upon partial or complete release of stresseson said spring means.

5. In an hydraulic machine, hydraulic motor means including main andpull-back cylinder chambers and ram means reciprocal therewithin, saidpull-back chamber being of less cross-sectional area than said mainchamber, and a hydraulic circuit comprising a reservoir tank, a pumphaving its suction side connected thereto, a pull-back valve connectedto the discharge side of said pump and connected to said pull-backchamber, an operating valve connected to said first-mentioned valve andalso connected to said tank and to said main chamber, said operatingvalve being operable in its closed position to cut ofi its connection tosaid tank, and said pull-back valve being operable in its closedposition to cut off its connection to said operating valve, andoperating means for alternately closing said valves, said operatingmeans including resilient means for urging said operating valve to itsclosed position, and a manually operable lever for stressing saidresilient means, each of said valves having fluid passages thereinenabling fluid under pressure from the associated chamber to open theassociated valve.

6. In an hydraulic machine, hydraulic motor means including main andpull-back cylinder chambers and ram means reciprocal therewithin,

said pull-back chamber being of less cross-sectional area than said mainchamber, and a hydraulic circuit comprising a reservoir tank, a pumphaving its suction side connected thereto, a pull-back valve connectedto the discharge side of said pump and connected to said pull-backchamber, an operating valve connected to said first-mentioned valve andalso connected to said tank and to said main chamber, said operatingvalve being operable in its closed position to cut oil its connection tosaid tank, and said pull-back valve being operable in its closedposition to cut off its connection to said operating valve, means forclosing said valves, and means including a manually operable lever foralternately actuating said last-mentioned means, each of said valveshaving fluid passages therein enabling fluid under pressure from theassociated chamber to open the associated valve.

'7. In an hydraulic machine of the class de scribed comprising hydraulicmotor means including main and pull-back cylinder chambers and ram meansreciprocal therewithin, said pullback chamber being of lesscross-sectional area 'than said main chamber, the combination of ahydraulic circuit comprising a reservoir tank, a pump having its suctionside connected thereto, a pull-back valve connected to the dischargeside of said pump and connected to said pull-back chamber, an operatingvalve connected to a port in said first-mentioned valve and comprising aport connected to said tank, said operating valve being connected tosaid main chamber, a stem in each valve for closing the portthereimresilient actuating means associated with said stems, and meansfor alternately operating the actuating .means of respective valves,each of said valves having fluid passages therein enabling fluid underpressure from the associated chamber to move the stem of the associatedvalve to open position.-

8. In an hydraulic machine, hydraulic motor means including main andpull-back cylinder chambers and ram means reciprocal therewithin, saidpull-back chamber being of less cross-sectional area than said mainchamber, and a hydraulic circuit comprising a reservoir tank, a. pumphaving its suction side connected thereto, a pull-back valve connectedto the discharge side of said pump and connected to said pull-backchamber, an operating valve connected to said first-mentioned valve andalso connectedto said tank and to said main chamber, said operatingvalve being operable in its closed position to cut off its connection tosaid tank, and said pull-back valve being operable in its closedposition to cut oil its connection to said operating valve, means forclosing said valves, and operating means for alternately actuating saidlast-mentioned means, each of said valves having fluid passages thereinenabling fluid under pressure from the associated chamber to open theassociated valve.

9. In combination, a hydraulic motor comprising advance and returnchambers of. relatively large and small cross-sectional areasrespectively, and ram means reciprocal within said chambers, advance andpull-back lines connected respec tively to said advance and pull-backchambers, pull-back valve means connected to said pullback line, meansfor actuating said valve means, operating valve means connected to saidadvance line, to said pull-back valve means, and to a discharge line,said operating valve means being adapted in the open position thereof todeliver hydraulic fluid to said discharge line, and said operating valvemeans being adapted in the closed position thereof to deliver hydraulicfluid to said advance line and to restrict flow of said fluid to saiddischarge line, and means for actuating said operating valve means, saidpull-back valve means being adapted in the open position thereof todeliver hydraulic fluid to said pull-back line and to said operatingvalve means, and said pullback valve means being adapted in the closedposition thereof to deliver hydraulic fluid to said pull-back line andto restrict flow of said fluid to said operating valve means, and asource of hydraulic pressure fluid connected to said pullback valvemeans, said last-mentioned actuating means including resilient means forurging said operating valve means to, the closed position thereofagainst thepressure of the hydraulic fluid therein, and manuallyoperable means for stressing said resilient means against the resistanceof said pressure in said operating valve means.

10. In a hydraulic machine, hydraulic motor means including advance andpull-back chambers of relatively large and small cross-sectional areasrespectively, and ram means reciprocal within said chambers, and ahydraulic circuit including a source of hydraulic pressure fluid,pull-back and operating valves connected to said pull-back and advancechambers respectively, said pullback valve being connected tosaidsource, and said operating valve being connected to said pullbackvalve, a discharge line connected to said operating valve, saidoperating valve being adapted in its closed position to restrict flow'offluid to said discharge line, said p ull-back valve being adapted in itsclosed position to restrict flow of said fluid to said operating valve,and operating means for alternately opening and closing respectivevalves in such manner that one ;of said valves is open when the otherthereof is closed. 1 ROBERT K. SEDGWICK.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number Fischer Feb. 9, 1943

